The invention is directed to a method for manufacturing a grooved cable drum shell, particularly for cable winches, reels, etc. to be wound with one or several layers. It is known, particularly for cable winches, to groove the drum shell in such a way that the wound cable is coiled with the individual strands spaced apart from each other 1 to 3 mm. This eliminates friction between adjacent coils during winding and unwinding. It is especially important to reduce the risk of wear in this manner when dealing with very long cables.
The grooving of the drum shell is generally done by means of machine tools. This method is very expensive and timeconsuming, particularly on large drums, due to the large amount of waste material. Also, expensive machine tools must be employed for this kind of work. In order to eliminate this problem, it has been suggested to wrap a cylindrical metallic drum shell core with a synthetic shell consisting of two cast, sprayed or pressed half shells, the exterior of such synthetic shell being provided with the appropriate grooves. This design for a grooved drum surface, however, is only rarely used as it is only practical for the manufacture of large quantities of small and medium sized drum shells in one production run. Moreover, since each mold can only be utilized for a certain drum diameter with a certain drum width and groove shape, the costs for tools and molds increase substantially as dimensions increase.
The invention is directed to a method for providing grooved surfaces for cable drums which is faster and, above all, cheaper than the conventional machining of grooves, and which may nevertheless be utilized for drums of all sizes, as well as different shapes of grooves, and even for small production runs. The invention provides a profiled rope or strand which is wound helically onto a cylindrical drum core, with one surface being provided with at least one longitudinal groove for rope and/or cable to be wound; and to fasten it to the drum shell core. This method permits the grooving at a fraction of conventional costs, at less time, and with practically no waste of material.
The profiled strand is connected in a detachable fashion at or near its ends with the shell core. This detachable connection, which is preferably done by means of screws, not only facilitates replacement of a worn strand with a profiled strand of the same type, but also allows for substitution of a profiled strand with a wider, slimmer or even double flute, if circumstances call for it.
Preferably, the strands of the invention are injection molded of a synthetic thermoplastic resin, although metal strands which are cast or extruded may be used also. The synthetic strands, however, are preferable, due to their much lighter weight and easier machinability. As the strands may be formed into very long lengths, coiled in bundles, waste is kept to a minimum.
It has been found appropriate, in accordance with the invention, to utilize at least two lengths of the profiled strands of the invention to provide a helically grooved surface on a drum core. By using more than one strand, a space may be provided where the ends of the two lengths join to accommodate longitudinal displacement or expansion of the strands on the core surface. To that end, the adjacent ends of the joined strands may be affixed to the drum surface through elongated holes or slots to accommodate this movement. Alternatively, one single, extremely long profiled strand may be attached to the drum shell core at proper intervals by means of two spaced apart screws, and thereafter a piece cut from the profiled strand between these two screws, the length of such piece corresponding to about the length of expansion expected from the separated profiled strand. In this manner, it is possible to wrap the drum shell core much faster and more exactly than would be possible with several shorter profiled strand sections. Preferably, the strands are reinforced by incorporating metal wire, metal strips or by textile or metal webs in order to reduce this expansion as much as possible.
The cross sections chosen as strand profiles may vary widely. One such strand profile, for example, is provided on one side with a continuous longitudinal slot, with the upper surface thereof tapering downwardly toward the edge in a wedge shape, whereas the other narrow side is provided with a corresponding integral ledge with an upper surface tapering upwardly toward the exterior in a wedge shape. When winding such a profiled strand, the adjacent sides are pressed firmly together due to the effect of the wedges, so that the coils are wedged together. Each strand coil is, therefore, tightly connected with its two neighboring coils laterally, while length expansion is not obstructed in any way. Other side edge profiles may be used to that end.
Before describing the invention in more detail, it may be well to note that various synthetic thermoplastics may be used to produce the strands of the invention, as will be understood by practitioners in the art, including, for example, polyesters and polyamides. With the foregoing objects in view, this invention will now be described in more detail, and other objects and advantages thereof will be apparent from the following detailed description of illustrative embodiments, the accompanying drawings and the appended claims.